The effects of the density profile on the power absorption and the equilibrium density in helicon plasmas

Power absorption profiles are computed using numerical integration for radially non-uniform helicon plasmas with finite axial lengths. As in a uniform plasma, the Trivelpiece–Gould mode dominates the power absorption causing the surface deposition of the rf power. In addition to the surface heating, there is bulk electron heating for non-uniform plasmas, and the portion of this bulk heating increases with the degree of the inhomogeneity. It has been also found that the radial inhomogeneity of the plasma density results in the suppression of the m=−1 mode and reveals the axial resonance condition. Finally, the global power balance is considered to estimate average equilibrium densities, which are found to be in agreement with experimental values.